Nice point, Wrong Stuff, I'm having to think about this. However, my quick-and-dirty answer is that lift is mainly suck from the upper surface of the wing. The other point is - try standing under a hovering helicopter or a Harrier - there's certainly a !!!!!load of air going downwards under them.
New Bloke - remember, if it's a closed system and you start blowing up balloons you'll just increase the pressure of the air that's trapped inside the aircraft - the weight remains the same.